From 2ffb5357e0e35d415311a40eea14e9cc99dd54ab Mon Sep 17 00:00:00 2001
From: Dominick Allen <dominick.allen1989@gmail.com>
Date: Sun, 28 Jun 2020 19:50:35 -0500
Subject: Improve read functionality.

---
 src/main.rs | 92 ++++++++++++++++++++++++++++++++++++++++++-------------------
 1 file changed, 63 insertions(+), 29 deletions(-)

(limited to 'src/main.rs')

diff --git a/src/main.rs b/src/main.rs
index c2f9881..0116f78 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -8,33 +8,59 @@ use rustyline::Editor;
 
 use lib::environment::Environment;
 
-fn read<T: rustyline::Helper>(rl: &mut Editor<T>) -> Option<String> {
-    let readline = rl.readline(">> ");
-    match readline {
-        Ok(line) => {
-            rl.add_history_entry(line.as_str());
-            Some(line)
-        },
-        Err(ReadlineError::Interrupted) => {
-            println!("CTRL-C");
-            None
-        },
-        Err(ReadlineError::Eof) => {
-            println!("CTRL-D");
-            None
-        },
-        Err(err) => {
-            println!("Error: {:?}", err);
-            None
+const EXIT_STRINGS: &[&str; 3] = &[",q", "exit", "quit"];
+
+fn read<T: rustyline::Helper>(rl: &mut Editor<T>) -> Result<String, String> {
+    let mut readline = rl.readline(">> ");
+    let mut full_line = String::new();
+
+    fn count_parens(s: &str) -> Result<bool, ()> {
+        let mut lcount = 0;
+        let mut rcount = 0;
+        for c in s.chars() {
+            match c {
+                '(' => lcount += 1,
+                ')' => rcount += 1,
+                _ => {}
+            }
+            if rcount > lcount {
+                return Err(())
+            }
+        }
+        return Ok(lcount == rcount)
+    }
+
+    let mut loop_count = 0;
+    loop {
+        match readline {
+            Ok(line) => {
+                full_line.push_str(&line);
+                match count_parens(&full_line) {
+                    Ok(true) => return Ok(full_line),
+                    Ok(false) => readline = rl.readline("... "),
+                    Err(_) => return Err("unexpected \")\"".to_string())
+                }
+            },
+            Err(ReadlineError::Interrupted) => {
+                return Err("user interrupt".to_string())
+            },
+            Err(ReadlineError::Eof) => {
+                if loop_count > 0 {
+                    return Err("end of file".to_string());
+                } else {
+                    return Ok(EXIT_STRINGS[0].to_string());
+                }
+            },
+            Err(err) => {
+                return Err(format!("{:?}", err));
+            }
         }
+        loop_count += 1
     }
 }
 
 fn means_exit(input: &str) -> bool {
-    match input {
-        "exit" | "quit" | ",q" => true,
-        _ => false
-    }
+    EXIT_STRINGS.iter().any(|&s| s == input)
 }
 
 fn eval(env: &mut Environment, input: &str) -> String {
@@ -45,8 +71,8 @@ fn eval(env: &mut Environment, input: &str) -> String {
 
     let res = lib::eval::eval(&sexp, env);
     match res {
-        Ok(x) => format!("{:?}", x),
-        Err(f) => f
+        Ok(x) => format!("{}", x),
+        Err(f) => format!("Error: {}", f)
     }
 }
 
@@ -61,12 +87,20 @@ fn main() {
     }
     loop {
         let input_line = read(&mut rl);
-        let line = match input_line {
-            None => break,
-            Some(expr) if means_exit(&expr) => break,
-            Some(expr) => expr
+        match input_line {
+            Err(e) => {
+                println!("Error: {}", e);
+                continue;
+            }
+            Ok(expr) => {
+                if means_exit(&expr) {
+                    break;
+                }
+                rl.add_history_entry(expr.as_str());
+                println!("{}", eval(&mut env, &expr));
+            }
         };
-        println!("{}", eval(&mut env, &line));
+
     }
     rl.save_history(hist_file).unwrap();
 }
-- 
cgit v1.2.3